In drilling, completion or service operations in a deviated well, it is sometimes important to be able to seal the tubing string mid-way to isolate production or other pressurized zones of the wellbore from surface.
In the past, tubing end-plugs have been used during injection of tubing into such a well, the plugs generally being a metallic or aluminum disc attached to the bottom of the tubing string prior to injection, and then the destruction of the metallic disc when the tubing string is located at bottom hole. This has the undesirable effect of leaving metal fragments at the bottom workface of the wellbore which is difficult or expensive to remove. These devices have only been run at the bottom of a tubing string, and cannot provide for dual sealing for tripping out of the wellbore.
Another mechanism sometimes seen is the use of an Otis® nipple, consisting of multiple profiles to receive a variety of plug devices via wireline delivery downhole. These mechanisms provide for a single plug, and while unpluggable and repluggable, are constrained by the plug delivery mechanism—that is, wireline plugs may be difficult to retrieve from deep deviated or horizontal wellbores, and may be impossible to inject and refit in non-vertical orientations. Additionally, if such a plug fitting fails during injection, the wireline plug may become a projectile, and two wireline plugs cannot or cannot easily be installed for the injection operations. Similarly, multi-profile landing nipples to receive a variety of plugs are manufactured under the Baker® trade name.
Frangible pressure seals such as disclosed in U.S. Pat. No. 5,924,696 are also known, but have not been deployed providing dual barriers during injection, nor do these devices themselves provide plug fittings, and have required the use of additional nipples or landings.
Thus, there is a need for a device to overcome the limitations of the prior art, in particular for use in deviated or non-vertical or horizontal wellbore situations.